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TTR: which gas?
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Posted by: jfurniss---------------------

I just bought a 1999 TTR-250, minus the owners manual. Is there a specific octane level recommended for this bike? I was planning on using just regular unleaded (about 87 octane I think)

Posted by: JWW---------------------

I always run the highest available octane. In CA its 91

Posted by: Frank in CO---------------------

I've been told by engineers on a Honda forum to run the lowest octane that doesn't cause knocking or pinging. Higher octanes are more volatile and create more engine heat and increase CO emissions. The lower octanes are better in the long run - except too low can cause serious damage.

Posted by: Frank in CO---------------------

One other option is to check your local library to see if they have a service manual for that model. Sometimes they have the Hanes or Clymer manuals. You could call the dealer and ask, or as a last resort you can order the owners manual for $30 or the service manual for $60 from Yamaha.

Posted by: Rich Rohrich---------------------

Quote:

Originally posted by Frank in CO
Higher octanes are more volatile and create more engine heat

All else being the same it's common for higher octane fuels to be LESS volatile because the components used to obtain the higher octane tend to be heavier and less willing to vaporize. Assuming the engine isn't knocking or running into pre-ignition there is no measurable heat difference between the highest and the lowest octane US pump fuels.

Posted by: Frank in CO---------------------

Ok, I stand corrected on the heat issue, but doesn't higher octane give off more vapor (i.e. the smell at the pump)? I think gasoline evaporates more quickly than diesel.

I guess the most important part is higher octane gets you no benefit once you past the engines optimum octane requirement so sometimes your just wasting money on premium unless you really need it for knocking issues.

Posted by: jfurniss---------------------

How low is too low? I run the 87 octane in my mowers, mix it for my 2 cycle weed eater and chain saw and run it in my truck. I bet it would be fine for my TTR, right? I'm a little cautious because 1) the bike is my NEW toy

and 2) if I only had one of the above mentioned vehicles running, it would be the bike (except when it rains - then I need my truck!)

Posted by: trailblaze---------------------

I have been running 87octane in my ttr-250 with out any problems. I also run 87 in everything I own from sleds to the car except I try and run premium in the weed wacker and chainsaw. I run a lawncare business so they get alot of use. My dealer says it helps them run cooler. I don't know how much I believe him since I probably put 300 hours on my last weed wacker running nothing but regular through it. I would say if you want to spend the extra money to put your mind at ease run the premium other then that I would run the regular. Just my opinion.

Posted by: Silum---------------------

hey, i just bought a 99 ttr-250 also and the manual says to use 87octane which is the lowest here in california, im sure thats really low for some of the other states. The ttr is a 4 stroke, you know that right? no need to mix the gas lol

Posted by: Rich Rohrich---------------------

Quote:

Originally posted by Frank in CO
Ok, I stand corrected on the heat issue, but doesn't higher octane give off more vapor (i.e. the smell at the pump)? I think gasoline evaporates more quickly than diesel.

Of course any gasoline evaporates more easily than diesel fuel. The distillation curve of pump gasoline is in the 80-400 F range while the range for diesel is 300-680F . Diesel fuel is a completely animal with a totally different chemistry than gasoline.

Posted by: Rich Rohrich---------------------

There is a real value to running higher octane fuel in an air cooled engine like the TTR. As the fins get covered with mud and dirt during a ride the internal temps go up and the octane requirement of the engine along with it. They ship these engines fairly lean to start with so you are not getting any real help from fuel to cool them, potentially pushing them closer to knock under high load situations (like load speed lugging) . Higher octane fuel provides a wider margin of safety.

It's your bike but it seems pretty foolish to me to cheap out a few cents on gas when you only use a few gallons a week.

Posted by: jfurniss---------------------

The bottom line seems to be that it is a matter of opinion. I tend to agree with Rich, however, that a few cents in price difference is cheap insurance. I just wanted to make sure Yamaha didn't specifically recommend staying away from any particular grade of gas.

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TTR: which gas?

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